Hydraulic energy sources for supplying a downstream hydraulic system with hydraulic energy are known.
In automatic transmissions, such as step-change automatic transmissions, continuously variable transmissions or dual clutch transmissions, with hydraulic control, i.e. actuator activation, such as clutch actuator or shift actuator control, and a cooling/lubricating oil supply, there is a need for an oil supply (generally a pump with a pump drive). In general, the pump drive is a mechanical pump drive, which is coupled to the internal combustion engine.
In modern transmissions, this mechanical pump drive can be supplemented by an electric pump arrangement (i.e. an electric motor with a pump).
The prior art also includes oil supply systems which manage without a mechanically driven pump for the transmission and clutch actuator systems. Here, however, there is no requirement for cooling oil owing to the construction of the clutch as a dry clutch.
If the intention is to dispense with a mechanical drive, especially in the case of wet clutches, all the hydraulic power required for this purpose must be provided by the electrically driven pump in the case of the known systems. However, there is great variety in the operating states which arise in this case. Thus, there are both situations involving a high volume-flow and a low pressure requirement and situations with a high pressure and a low volume-flow requirement. These completely different boundary conditions necessitate very large electric motors (costs, weight, load on the onboard electrical system) in the case of a conventional electric motor/pump arrangement (speed-controlled drive) in order to provide the different operating states in an oil supply system.